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What is it? Overview Usage Side Effects and Warnings

What is Melatonin?

Melatonin is a natural hormone that regulates sleep. During daylight, the pineal gland in the brain produces an important neurotransmitter called serotonin. (A neurotransmitter is a chemical that relays messages between nerve cells.) But at night, the pineal gland stops producing serotonin and instead makes melatonin. This melatonin release helps trigger sleep.

The production of melatonin varies according to the amount of light you're exposed to; for example, your body produces more melatonin in a completely dark room than in a dimly lit one.

Melatonin supplements appear to be helpful for people whose natural sleep cycle has been disturbed, such as travelers suffering from jet lag. The hormone may also be helpful in various other sleep disorders.

Based on early...

Reasonably good evidence tells us that melatonin can help people with jet lag adjust to a new schedule. 1 Although it probably works in part by resetting the biological clock, it also appears to decrease or block wakefulness-promoting circuits in the nervous system 2 and may have other direct sedative effects. Based on this, melatonin has been tried for insomnia of various types, but results have been inconsistent 3 .

Three small double-blind studies suggest that use of melatonin might reduce symptoms of irritable bowel syndrome . 4 It has been suggested that melatonin might work through effects on the nervous system in the digestive tract.

Four double-blind studies performed by Saudi researchers reported that melatonin was useful for reducing anxiety prior to surgery,...

Safety Issues

A safety study found that melatonin at a dose of 10 mg daily produced no toxic effects when given to 40 healthy males for a period of 28 days. 5 However, this does not prove that melatonin is safe when taken on a regular basis over the long term. Keep in mind that melatonin is not truly a food supplement but a hormone. As we know from other hormones used in medicine, such as estrogen and cortisone, harmful effects can take years to appear. Hormones are powerful substances that have many subtle effects in the body, and we're far from understanding them fully. While in one small study, use of melatonin over an 8-day period by healthy men did not affect natural release of melatonin or levels of pituitary or sex hormones, 6 another study found effects on testosterone...